Boundaries, demarcation lines (6)
I believe the answer is:
limits
This clue is a double definition.
'boundaries' is the first definition.
(I know this)
'demarcation lines' is the second definition.
('limit' can be a synonym of 'demarcation line')
(Other definitions for limits that I've seen before include "Sets boundaries to, restricts" , "Points beyond which one may not go" , "Boundaries, confines" , "Curtails" , "Frontiers" .)